JPS58205620A - Pipe bending device - Google Patents

Abstract

PURPOSE:To obtain a bent pipe of small thickness reduction without generating defects in the worked product by providing a means that applies axial compressive force corresponding to the angle of pipe bending during the work in a device that rotates a bending die relatively to the pipe to be worked. CONSTITUTION:A pipe 2 is fixed to a rotary die 5 by a clamp 6, and bent with rotation of the die 5. At this time, bending is performed while applying axial compressive force F from the rear end of the pipe 2 by a hydraulic actuator 7. To control the compressive force, the angle theta of rotation of the die 5 is converted to an electric signal by a potentiometer 8 attached to the rotation shaft, digitized by a converter 9 and reads out a prescribed axial force signal from a memory 10 by using this as a reference signal. After analogizing this again by a converter 11, it is given to an amplifier 12 as a reference value for controlling. On the other hand, oil pressure from a hydraulic source 13 is controlled by a valve 14, and above-mentioned compressive force F becomes an electric signal through a cell 15, amplified by a strain gauge 16 and fed back to the amplifier 12. Force F applied to the pipe 2 is controlled by above-mentioned controlling loop according to the angle theta.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a metal tube bending device.
In particular, in this device t, i! due to bending! This invention relates to an effective mechanism for preventing local thinning of the f-wall.

Conventionally, when bending pipes, V! It is known that bending while applying compressive force in the axial direction of the pipe is effective in preventing local thinning of the wall l).

Based on this principle, the pressure die l is moved in the bending process fi shown in FIG. . In this configuration, the frictional force between the pipe 2 and the pressure die 1 acts as an axial compressive force on the pipe 2, but due to variations in the frictional force, an appropriate axial compressive force may not necessarily be generated. I couldn't.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a pipe bending device that can eliminate the above-mentioned drawbacks.

In order to achieve the above object, the present invention provides an axial compressive force applying means that can control the magnitude of the compressive force applied in the axial direction of the pipe during bending to an appropriate value corresponding to the bending angle of the pipe. The invention is characterized in that it is possible to obtain a curved pipe with a small decrease in wall thickness without causing defects in the processed product.

That is, in the present invention, a means for detecting the rotation angle is provided on the rotating shaft of the bending die of the bending machine, and a force of a predetermined strength is applied to the rear of the pipe according to the detected rotation angle signal. By adding to the above, the above objectives were achieved. In particular, a small pressure force is applied at the beginning of bending when the compressive force exceeds a certain value, which tends to cause buckling of the pipe wall, and a large compressive force is applied during the latter half of the bending, when the wall thickness reaches its minimum value. 9 baits are processed into bent pipes with no defects and little thinning.

Hereinafter, the present invention will be explained in detail with reference to the embodiments shown in FIGS. 2 and 3. FIG. 2 shows a cross section of the mechanism of the bending device according to the present invention.

In the figure, a pipe 2 is fixed to a rotary die 5 by a clamp 6 and is bent as the rotary die rotates 50 times. At this time, bending is performed while applying compressive force in the axial direction with the hydraulic actuator 7 from the rear end of the pipe 2. The compression force at this time is controlled according to the signal block diagram shown in FIG. The rotation angle θ of the die 5 is converted into an electric signal by a potentiometer 8 attached to the rotation axis, and A
/D converter 9 digitizes the data. Using this as a reference signal, a predetermined axial force signal is read out from the storage device mio, and the D/A
After converting to analog again with the converter 41, the servo amplifier 12
is given as a reference value for control.

- the hydraulic pressure supplied from the hydraulic source 13 is controlled by a servo valve 14 and drives the hydraulic actuator 7; The axial compressive force F applied to the pipe 2 by the actuator 7 becomes a warm-up signal via the load cell 15, and the strain gauge 1
6 and fed back to the servo amplifier 12. Through the control loop described above, the axial compressive force F applied to the pipe 2 is controlled according to the rotation angle θ of the die 5.

Next, the effect of controlling the axial compressive force F applied to the pipe 2 will be described. Figure 4 shows the #1 wall along the bending outer periphery of the pipe 2 subjected to bending force (indicated by the angle ψ of the clamp 6 side force λ)
3 is a graph showing the results of measuring the wall thickness distribution of . Axial compressive force Ft - When not applied (curved person), the enemy's strength is about 24%
Thickness is seen. On the other hand, in the case of processing using the conventional booster 4 as shown in FIG. 1 (curve B), the maximum value of thickness reduction is reduced to about 20%. On the other hand, when bending is performed by controlling the axial compressive force F according to the present invention (curve C)
In this case, the thickness reduction was reduced to about 16%, which was a much better result than the conventional Booster 4.

The reason for this is that in the conventional booster 4, the necessary and sufficient axial compressive force F cannot be applied because the axial compressive force F depends on the frictional force between the pressure die 1 and the knob 2. There is. On the other hand, in the processing apparatus according to the present invention, it is possible to generate a necessary and sufficient axial compressive force Ft7111 corresponding to the bending angle l of the die 5. θ=180°
Taking bending as an example, the control mode of the axial compressive force F corresponding to the bending angle of the die 5 of 0 is shown in FIG. Noku Eve 2
The maximum value of the axial compressive force F that can be applied from the rear end is determined by the buckling limit of the straight pipe. If this maximum value is Fo, then
For the purpose of preventing wall thinning, it is desirable to apply an axial compressive force F as close to Fo as possible to the pipe 2.

However, if the axial compressive force F is large at the beginning of 50 rotations of the bending mold, buckling will occur in the wall of the pipe 2 due to bending, and a good product will not be produced. Therefore, as shown by the solid line in FIG.
The mode in which the axial compressive force F is gradually increased until reaching
It was also found that the conditions for moths were such that there was little thinning and no buckling occurred.

Incidentally, such a control mode for the axial compressive force F can be set arbitrarily according to the purpose of machining, and the control mode can be changed overnight using the storage device (read-only memory) 10 shown in Fig. 3. This is easily possible by simply rewriting .

As described above, according to the present invention, when bending a pipe, it is possible to appropriately apply a necessary and sufficient axial compressive force as the pipe bends. This has the effect of preventing thinning of the tube wall along the bending outer periphery. Furthermore, by increasing the axial pressure force t in accordance with the rotation angle of the bending die, it is possible to prevent buckling of the tube wall, which conventionally tends to occur at the beginning of bending.

As a result of obtaining a device that bends pipes with a uniform wall thickness over the entire length of the pipe and without creating unevenness on the pipe wall, it is possible to create pipes with light lids and thin walls with little extra wall thickness in equipment with pipes. design is now possible. By doing so, we achieved great industrial benefits, such as improving the performance of these devices and reducing the amount of material used for pipes.

Note that although the fluid force was originally exemplified by controlling the axial compressive force by a hydraulic servo system, it goes without saying that the same effect can be obtained even if this is replaced with an electric/mechanical system.

References l) Endo et al.: Plasticity and processing vol, l 9 421
2 (1978, 9) p742 2) Ba51c 'pube 13 ending
Quide H&HTOOID Division (De
nve'+C"'-5UsA) 3) Nakamura, Sasaki Nigelesu Gijutsu vol, 12 4B (1974) 999

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the action of the axial clamping force applying means in a conventional rotary drawing machine, FIG. 2 is a sectional view showing an embodiment of the bending device according to the present invention, and FIG. A signal block diagram showing one method of axial force control according to the invention,
FIG. 4 is a diagram comparing the wall thickness distribution of a pipe processed by the bending machine of the present invention with that of a conventional pipe, and FIG. 5 is a diagram showing an example of the control mode of the axial compressive force in the 021808 bending process. 1... Pressure die, 2... Workpiece pipe,
3...Arrow indicating the driving direction of the pressure die, 4...
・Booster for driving the pressure die, 5...
Rotating die, 6... Clamp die, 7... Hydraulic actuator, 8... Rotation angle adjustment potentiometer, 9
... A/Di conversion, 10... Storage device t (!J-do only memory), 11... D/A converter, 12.
...Servo amplifier, 13...Hydraulic pressure source, 14...Hydraulic servo valve, 15...Load cell, 16...Strain meter, 1
7...Shinkin-o agent usually used for rotational handling. Patent attorney Toshiyuki Usuda ■ 1 Figure 'f, z Figure abolished J Figure 13 fJ 4 Figure

Claims (1)

[Claims] 1. In a device that bends the pipe by rotationally moving a bending die relative to the pipe as a workpiece, an axial compressive force corresponding to the rotation angle of the bending die is applied to the pipe. A pipe bending apparatus characterized in that the pipe is bent while applying an axial compressive force by the applying means. λ The pipe bending apparatus according to item 1, wherein the applying means is set so that the axial compressive force applied to the pipe is smaller at an initial stage of rotation of the bending mold than thereafter. The applying means extracts the rotation angle of the bending plate as an electrical signal, uses this as a reference signal, outputs a signal corresponding to the force to be applied to the pipe from the memory am, and uses this signal as a reference value to apply the force to the pipe. How to control <*h! i
1. The pipe bending device according to item 1, characterized in that: